"Since the 1600s, chocolatiers have been perfecting the art of the bonbon, passing down techniques for crafting a perfectly smooth, even chocolaty shell."

'The research should also have uses far beyond the chocolate shop: By knowing just a few key variables, engineers could predict the mechanical response of many other types of shells, from small pharmaceutical capsules to large airplane and rocket bodies. The team’s results are reported today in the journal Nature Communications.

'The researchers developed a fabrication technique to quickly create thin, rubbery shells, which involved drizzling liquid polymer over dome-shaped molds and spheres such as ping pong balls. They allowed the liquid to coat each mold and cure, or solidify, over 15 minutes. They then peeled the resulting shell off the mold and observed that it was smooth — virtually free of noticeable defects — with a nearly uniform thickness throughout.

'Combining this simple technique with the theory they derived, the team created shells of various thicknesses by changing certain variables, such as the size of the mold and the polymer’s density. Surprisingly, they found that the shell’s final thickness does not depend on the volume of liquid or the height from which it is poured onto the mold.'